Apparatus for centering shanks in casting diamond bits



Dec. 17, 1946. M; 1.. TUCKER APPARATUS FOR CENTERING SHANKS IN CASTING DIAMOND BITS Filed Nov. 9, 1944 to cast the bits.

Patented Dec. 17, 1946 APPARATUS FOR CENTERING SHANKS IN CASTING DIAMOND BITS Mana L. Tucker, Detroit, Mich., assignor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application November 9, 1944, Serial No. 562,227

(Cl. 225S) 3 Claims. I This invention relates to apparatus for casting composite diamond bits.

The main object of the invention is to provide apparatus containing a'die in which the diamonds are properly supported for casting metal or alloy to encompass them and having means for. accurately centering a bit blank over the diamonds so that the resulting cast bit will run true during drilling.

Aiurther object is to provide such a simple apparatusfor casting diamond cutting and drilling bits that only very few parts are required to be assembled to form. the mold for casting, and, after casting, to be taken apart torelease the cast bit.

, Other objects and the advantages of the invention are set forth more fully in detail in the following specification in conjunction with the accompanying drawing, in which:

Fig. 1 is a vertical section of the entire apparatus with a complete cast diamond bit in place;

Fig. 2 is a vertical section of the cast bit after release from the mold and before trimming;

Fig. 3 is a similar view of the castbit after the excess cast metal has been trimmed oil;

Fig. 4 is a vertical section of the bit blank alone before applying cast metal or attaching diamonds thereto;

Fig. 5 is another view of the same bit blank as seen from the bottom in Fig. 4;

Fig. 6 is a'plan view of the main die of the apparatus; and

Fig. '7 is a transverse section of the same die taken along the line 1-1 in Fig. 6.

Heretofore the practice of setting and casting diamonds in a group to form a diamond bit has frequently entailed the use or more or less complicated apparatus requiring a large outlay not only for the equipment but also for skilled labor In some cases the bits were made by makeshift methods and means in connection with which the molten metal was first cast and then mounted separately on the bit blank with the result that all too often the metal holding the diamonds and the bit blank did not run concentrically.

In order to overcome these and other disadvantages and particularly with the foregoing objects in view, it is now contemplated to hold the bit blank in true concentricity with a portion in a die serving to support the diamonds and receive the molten metal as will now be set forth in detail.

Hence, referring again to the accompanying drawing the bit blank In (Fig. 4) is mounted on a centering plug or stud H and a holding cap I2 is passed down upon the plug and screwed upon thread 13 of the bit blank until the upper end of the latter engages against a radiallyextending locating flange or projection l 4 and also shoulder I5 of the cap engages against the same flange from above. At the same time the lower end is of the holding cap rests against shoulder 11 on the bit blank, the latter and the holding cap as well as the centering plug are thus held in rigidly assembled relation;

The die or holder 18 is placed in position upon the vacuum chamber I 9 so as to rest in the'recess 2| in the upper part of said chamber. The mentioned die has an annular groove22 (Figs. 6 and 7) open to the top witha generally concave bottom 23 perforated by a plurality of holes 24 extending down to the lower surface 25 of said die and at their upper extremities being adapted to seat the cutting diamonds 26. The vacuum chamber l 9 is connected to an exhaust pump (not shown) by pipe 2? and the pump started so that a partial vacuum is created in chamber L9. The diamonds are individually seated in the upper ends of holes 24 so that the entire bottom 23 central aperture 29 in the die 25 which is con-' I centric with the annular groove 22 so that the plug stands upright with its shoulder 3| resting on the die upon the annular area 32 around said central aperture, thus ensuring the concentricity of the bit blank with the groove. The flask ring 33 is also placed in position with its lower recess portion 34 fitted upon the top 35 of the die and the molten metal or alloy 36 poured into the upper concave portion 31, and flowing down over and encompassing the diamonds 25 and also passing through anchoring holes 38 in the lower reduced portion 39 of the bit blank. The suction prevents the diamonds 26 from rising under the buoyant force of the metal which has a greater specific gravity. As soon as suflicient casting metal has been poured, the exhaust pump is sembled the following procedure may be carried out.

- When the casting is suficientl'y cool the die [8 and the ring 33 as well as the casting and the bit blank assembly are removed from the vacuum chamber and the die cautiously removed from the casting andthe flaskring, after which the latter is removed. Then the holding cap I2 is unscrewed from threads IS on the bit and removed from the centering plug II, and thereafter the latter is withdrawn from within the bit, with said bit appearing substantially as shown in Fig. 2. The cast metal 4|, 42 is trimmed off preferably by turning in a lathe to produce a finished bit as shown in Fig. 3, wherein it is evident that the major E01:- tion of the cast metal 36 above the portion thereof actually holding the diamonds has been out substantially to the inside and outside diameters 43 and 44 of the bit blank to provide drillingclearance for the bit.

- An example'of an alloy suitable for use as the casting metal 36 consists of 2 percent beryllium, 0.35 percent nickel and the remainder copper.

In drilling the holes 38 it is often found desirable to remove the metal between the round hole (which is illustrated) and the lower face of the reduced extension 39 of the bit blank, thereby forming a series of downwardly open slots or grooves. The advantageof the open slots is that they. permit the molten metal to flow therethrough more rapidly and with less cooling effect, as compared with the closed holes 38.

What is claimed is:

1. Apparatus for casting anaccurately centered diamond drill bit comprising a die having an an nular recess perforated at the bottom for individually seating a plurality ofdiamonds and a central aperture, means cooperating with said die for receiving and retaining molten metal in association therewith during casting, means for producing suction through the perforations in said annular recess past said diamonds to retain the latter in position, a centering plug. having a body portion adapted to extend through and sup.-

port a bit blank in predetermined position above thedieand terminating at one end in a central tip of reduced diameter, said central tip being adapted to fit into the central aperture in said die concentric with the annular recess therein, and means upon said centering plug for locating said bit blank a predetermined distance from said an,- u a ess d r sthe c s n o erat 2. Apparatus for casting an accurately centered diamond drill bit comprising a die having an annular recess perforated at the bottom for individually seating a plurality of diamonds and a central aperture, means cooperating with said die for receiving and retaining molten metal in association therewith during-casting, means for producing suction through" the perforations in said annular recess past said diamonds to retain the latter in position, a centering plug having a body portion adapted to extend through and support a bit blank in predetermined position above the die and terminating at one end in a central tip of reduced diameter, said central tip being adapted-to fit into the central aperture in said die concentric with the annular recess therein, a locating projection fixed upon the body portion of the centering plug and serving as a stop for locat- 3. An apparatus for casting an accurately cen:

tered diamond drill bitcomprising vacuum ,oharn, ber means, a die supported on the vacuum cha ns ber means and in communication therewith, said die having an annular recessv perforated. at the bottom for individually seating a plurality of diamonds and a central aperture-concentric there; with, a flask ring supported on the die a ai st lateral displacement relative thereto and adapted to receive and retain molten metal during the casting operation, a centering plug adapted to slidably support a hollow externaly threaded bit blank in a predetermined position above the die, said plug having a pilot portion located in the central aperture of the die to position the blank concentric with the annular recess therein, said plug having a radially-extending flange serving. as stop for locating the bit blank upon'the plug, and an internally threaded removable cap passed down upon the plug and adapted to cooperate with the flange and the externall threaded bit blank to locate and retain the bit blank in a proper position relative to the annular recess of the die during the casting operation,

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